I may seem like a fuddy-duddy to some other parents with the ~somewhat~ early (or at least not late) bedtimes we have established for our grade school aged kids during the week, but the further I go, the more I believe we're doing the right thing. I may not be able to control whether they get sick or not, or if they always eat all their veggies, but the one thing I CAN make sure of is that they always get a good night's sleep. And the older they get, the more important the benefits of being well rested are, considering the increasing academic rigor that comes with the higher grades. Considering how sleep deprived most kids are, they'll be Well Rested Supermen by the time they arrive at high school.
And I've already tried to instill in them that all-nighters to cram for an exam are, without a doubt, absolutely counter-productive. Been there, done that - fell asleep during a Physics final. Staying up all night to try and learn a semester's worth of material simply doesn't work. If you haven't done the work all along and don't know the material before the final arrives, adding a serious level of fatigue won't help.